The Olympian also opened up about becoming a mom and what she would be doing if she wasn't playing tennis.
Serena Williams had to keep her cameo in Beyoncé's Lemonade secret for months.
"If you tell me, 'Don't say anything,' I won't say anything," she said in a WSJ Magazine profile of her epic -- and, in retrospect, long-awaited -- debut as a video girl alongside Queen B in "Sorry." (Seriously, she is so good at twerking. Why did we wait so long to get Williams in a music video?)
Even now, she's not saying much, only explaining her presence by stating, "I've known Bey for a long time." And of her top tier, five-star twerking abilities, admits, "I got really sore from dancing!"
The 34-year-old athlete did open up about what she would be doing if she wasn't the best tennis player in the world and about starting a family -- she recently told Glamour magazine that she's "far too young" to have kids right now.
"Being a mom would be fun," Williams said, revealing with a laugh that she wants, "Twelve. A baker's dozen."
While Williams will soon defend her reign as Wimbledon champ before competing in the Rio Olympics, she can imagine an alternate life that involves a far different career choice.
"I think I would be in California. Maybe I would be married? Maybe I would have kids? I would like to believe I would," she pondered. "I would have probably gone into some kind of science. I love animals. Maybe I would have become a veterinarian."
Bonus fun fact: Serena Williams does not watch Game of Thrones. She told the magazine, "I saw the first five minutes, and I was like, 'This is waaaaay too much for me.'"
Meanwhile, Bey recently stole the show at the NBA finals, smiling courtside with Jay Z and hilariously responding to her viral side eye. Check it all out in the video below!